More than 3,000 people have been killed in the last quarter century - and more - of atrocity and pain in Northern Ireland. But the events of Bloody Sunday, January 30th, 1972, remain a defining moment, when the trust and confidence of the nationalist community in the British government, in the Northern state and in their security forces were fundamentally and wholly undermined. For the relatives of those who died it has been a long and painful journey from those events on that Sunday in Derry twenty-six years ago to yesterday's Commons statement by the British Prime Minister, Mr Blair, in which he announced a new tribunal of inquiry. Inevitably, there may be some scepticism that none of the three-member tribunal team - to be chaired by Lord Saville - is likely to be drawn from outside the Commonwealth. There will be resentment among some that no formal apology has yet been tendered by the British Government. That said, Mr John Hume, who was present on that fateful day in Derry, is surely right to applaud the Prime Minister for his efforts to establish the full truth about what happened on Bloody Sunday. The purpose now is to ascertain the truth. Nor should undue emphasis be placed at this stage on the question of immunity from prosecution for former officers and soldiers. The critical issue now is whether the tribunal team has the powers it requires and the political backing it must have to establish the facts. There are good grounds for optimism. The inquiry, like the Widgery Tribunal before it, will have the authority to subpoena witnesses and to compel the disclosure of documents. The critical difference is that it is being established in a spirit of openness by a government apparently determined to establish the truth - even if this discommodes members and former members of the security establishment. The contrast with the political climate which generated the Widgery Tribunal - established on the day after Bloody Sunday and concluded some 11 weeks later - could scarcely be more complete. The 178-page Government report on Widgery and the new evidence, initiated by the government of former Taoiseach, Mr Bruton, and published yesterday, provides the most damning assessment of the 1973 tribunal. With forensic precision, the report assembles persuasive evidence to support its contention that Widgery was seriously flawed and "startlingly inaccurate and partisan" in its version of events. The hope is that the new tribunal will succeed in establishing an accurate historical record and thereby help to reduce the pain of all of those affected by Bloody Sunday; that it will help to remove what the former Bishop of Derry, Dr Daly, has called a "festering sore" in Derry and beyond it. But a thorough-going inquiry which establishes the full truth can also achieve a wider purpose; what Mr Blair called a " way forward to the necessary reconciliation which will be such an important part of building a secure future for the people of Northern Ireland." It can, in a still bitterly divided society, form part of the necessary healing process.